Preheat oven to 350°F and grease a 9"x5" loaf pan with cooking spray.

With a mixer, combine butter and sugar together. Add eggs and vanilla and beat until smooth, about 2 minutes.

Smash 2 ripe bananas with a fork in a small bowl. Add to butter mixture.

Prepare 1/3 cup instant coffee with water, add to butter mixture. Add sour cream and blend until smooth.

Sift together whole wheat flour, cocoa powder, baking soda, baking powder, and salt. Gradually add flour mixture to butter mixture, beating on medium speed for 2 minutes or until fully combined.

Pour mixture into prepared loaf pan. Bake for 45 minutes or until a wooden pick inserted in the center comes out cleanly.

Cool for at least 10 minutes in the pan before removing the loaf. Cool completely on a wire rack before attempting to slice or the loaf will crumble.